Embodiments of this invention relate generally to electrocardiograms (ECGs) and more particularly to analyzing ECGs to diagnose ventricular fibrillation.
ECGs depict electrical activity of the heart over time. Electrical activity is detected by electrodes placed at different locations on the body. The 12 lead ECG is well known to those skilled in the art. Each lead depicts electrical activity along a distinct axis of the heart. Electrical activity in the heart stimulates contraction of the heart muscle, resulting in a cycle of contraction and relaxation. The electrical activity associated with these contractions may be visualized with an ECG, providing information about the activity of the heart muscle.
Referring to FIG. 1, a schematic representation of one known contraction of a heart within normal limits is shown. A contraction 10 of the heart with a normal sinus rhythm may result in generating a P wave 12, a Q wave 14, an R wave 16, an S wave 18, and a T wave 20. With respect to a cardiac rhythm, a QRS complex 22 represents a rapid contraction of the ventricles of the heart. A person skilled in the art will readily recognize these features and others of the normal sinus rhythm. A person skilled in the art will readily recognize that the heart within normal limits may exhibit many variations on the representation shown in FIG. 1 and that a skilled diagnostician may be needed to distinguish these variations and what those variations represent.
Referring to FIG. 2, a schematic representation of a known rhythm strip of an ECG of the heart within normal limits is shown. The known rhythm strip shows electrical activity of the heart over time. A series of ventricular contractions 24 and relaxations 26 may be seen on the known rhythm strip. Referring to FIG. 3, a schematic representation of a known rhythm strip of the heart within normal limits is shown. A series of ventricular contractions 24 and relaxations 26 may be seen on the known rhythm strip. In comparison to FIG. 2, the contractions shown in FIG. 3 are less distinct but the relaxation 26 between the contractions 24 may be distinguished from the contractions 24. A person skilled in the art will readily recognize that the heart within normal limits may exhibit many variations on the representations shown in FIGS. 2 and 3 and that a skilled diagnostician may be needed to distinguish these variations and what those variations represent. Diagnosing a ventricular rhythm of the heart may be useful for deciding whether to provide emergency intervention to a person. Ventricular fibrillation (VF) is a leading cause of death in the developed world. The standard of care for VF is to initiate cardiopulmonary resuscitation (CPR) and, when available, attach an external defibrillator to deliver an electrical shock. An automated external defibrillator (AED) may be used to administer an electrical shock to the person. Prior to allowing the administration of the electrical shock, the AED may require that VF be detected. Current AEDs may require cessation of CPR and a delay of up to twenty seconds in order to diagnose a ventricular rhythm. In the person requiring defibrillation, the delay of up to twenty seconds may decrease the chance of resuming spontaneous circulation and lower the probability of neurologically intact survival.
Referring to FIG. 4, a schematic representation of a known rhythm strip of an ECG of the heart with ventricular fibrillation is shown. In VF the ventricles contract in an uncoordinated fashion. The ventricles exhibit essentially continuous activity with different parts of the heart muscle depolarizing at different times, and the ECG does not show distinct ventricular contractions 24, FIGS. 2, 3 or recognizable ventricular relaxations 26, FIGS. 2, 3 (quiescent periods). Under the circumstance represented by FIG. 4, the heart's ventricles may be contracting relatively continuously and the individual may be diagnosed as suffering from ventricular fibrillation (VF).